Design Home Fundamentals Introduction 2D Datums 2D Hole/Shaft 2D Bonus Tolerance 2D Bon Tol Example 2D Virtual Condition 3D Datums 3D Hole 3D Bonus Tolerance 3D Virtual Condition 3D Functional Gauge Reference Symbols Parallel vs Flat Cylindrical Specs Acceptance Resources Bibliography
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 3D Virtual Condition The Virtual Condition of a feature is a concept used to describe the worst-case envelope within which either of two features must lie in order to mate acceptably. For a shaft that fits into a hole, the shaft virtual condition must be smaller than the hole virtual condition. We had discussed this topic in the section 2D Virtual Condition. The concepts and illustrations are the same since tolerance zones and virtual condition boundaries now simply become 3D right circular cylinders that project out of the page. As we had seen for the 2D case, for an external feature of size, such as a shaft, the virtual condition is equal to the size at MMC plus the size of the tolerance zone. For the shaft in Figure VC1.1, the diameter of the virtual condition is the diameter of the MMC shaft plus the diameter of the position tolerance zone. Figure VC1.1 For an internal feature of size, such as a hole, the virtual condition is equal to the size at MMC minus the size of the tolerance zone. For the hole in Figure VC1.2, the diameter of the virtual condition is the diameter of the MMC hole minus the diameter of the position tolerance zone. Figure VC1.2 Figure VC1.3 shows the shaft and hole virtual conditions superimposed. Since the shaft virtual condition is smaller than the hole virtual condition, the two parts will always mate. Figure VC1.3 In summary, the way to calculate virtual condition (VC) for a shaft and hole is: SHAFT VC = MMC diameter + Position Tolerance Zone Diameter HOLE VC = MMC diameter - Position Tolerance Zone Diameter Virtual condition is extremely useful in the design of functional gauges. A functional gauge made to conform to virtual condition will ensure that a part will always mate with its counterpart. See 3D Functional Gauge.
Metal 3D Printing Design Guide

Direct Metal Laser Sintering (DMLS) 3D printing for parts with reduced cost and little waste.

Injection Molding Design Guide

Guide for high quality and cost-effective plastic injection molding.

STEM Career Outlook

Wages, employment opportunities, and growth projections for STEM jobs.

Selecting the Right 3D Printer

Discover how to choose the right 3D printer for your needs and the key performance attributes to consider.